There is a known virtual slide in which a plurality of sets of partial image data formed by acquiring images of parts of a specimen on a slide glass with a microscope at high resolution are connected together to obtain image data of the entire specimen, and this image data is displayed on a PC display or the like and can be observed as a microscope image.
In the case where an image is acquired in a microscope, shading occurs, which means brightness variations that arise due to variations in the light source, nonuniformity in the optical system, variations in the image-acquisition device and so forth. Shading becomes darker farther from the optical axis, and therefore, when a plurality of sets of partial image data are connected, as with a virtual slide, unnatural boundaries occur at the boundary areas in each set of partial image data, and the shading itself appears to be a pattern on the specimen.
In addition, shading has the property that it changes depending on the reflection and scattering characteristics of the specimen and therefore must be corrected for each specimen according to the characteristics of that specimen.
Therefore, there are microscope systems that prepare a correction gain, which is a shading correction value, in advance and perform shading correction on the basis of this correction gain. As an example of such a microscope system, Patent Literature 1 discloses an apparatus in which a correction gain is obtained on the basis of a change in brightness of an image in which a prescribed location on the specimen is acquired at the center of the viewing field and an image in which that same location is acquired at the edge of the viewing field, and shading correction is performed on the basis of the thus-obtained correction gain.